"It doesn't mean you can win the marathon or clean and jerk 750 pounds or win a cycle sprint," said the South Florida resident, 56. "It's not about getting there sooner." Tai chi is more about how the body works than how it looks, and is about aging gracefully and "with less drama."

"The last time I looked, there were some 500 studies about the various physical benefits of tai chi, from improving balance and attention span to boosting the immune system to beating back the symptoms of arthritis, asthma and insomnia," said Rosenfeld.

The practice is not perfect. Tai chi "does not supply the cardiovascular component that we'd be looking for in a well-rounded routine," said Jessica Matthews, a San Diego, California-based exercise physiologist. "The exertion level, while challenging, is not going to increase your heart rate."

'Grand ultimate motion'

T'ai chi ch'uan, as it is formally known, derives from a form of Chinese martial arts. Explaining the slow, circular movement of the practice, Rosenfeld said tai chi is a philosophical term that means the harmonious interplay of opposing forces.

When nature encounters a strong force, the way it answers that force to maintain harmony in the world is with a spiral, he said. "Astronomers see galaxies moving in spirals, water goes down the drain in a spiral, tornados form as a spiral. We spiral in tai chi because the most effective way to move fluid through solid is a spiral."

Hawaii-based personal and group-fitness trainer Jordan Forth, who has studied tai chi since 2006, said one translation of tai chi is "grand ultimate motion."

"I recommend it to everybody," said Forth. "It teaches people to move well in multiple planes of motion with a state of awareness not cultivated in everyday fitness. Most people check out on a treadmill or during high-intensity activity."

Forth said tai chi improves mobility, movement and flexibility and can be even more dynamic than yoga, which the 35-year-old has studied since he was a teenager.